Evaluation of Testing Uncertainties for the Impact Resistance of Machine Guards

2021 ◽  
Author(s):  
Luca Landi ◽  
Eckart Uhlmann ◽  
Robert Hoerl ◽  
Simon Thom ◽  
Giuseppe Gigliotti ◽  
...  
Keyword(s):  
Probabilistic Approach ◽  
Impact Resistance ◽  
Impact Testing ◽  
Ductile Material ◽  
Projectile Energy ◽  
Ballistic Limit ◽  
Worst Case ◽  
Impact Tests ◽  
Velocity Reduction ◽  
The Impact

Abstract Machine guards provide protection against ejection of parts during operation, such as chips or workpiece fragments. They are considered safe if the impact resistance is at least as high as the resulting projectile energy in the worst case of damage. To protect the machine operator, the impact resistance of machine guards is determined according to ISO standards. The bisection method can be used to determine the impact resistance through impact tests. However, this method is inaccurate for a small number of impact tests and does not provide an indication of uncertainties in the determination. Moreover, the result of testing is validated in different ways depending from the standard utilized for testing.Relevant uncertainties affecting impact testing and a new probabilistic approach for assessing the impact resistance using the Recht & Ipson equation are presented. With multiple impact tests at different initial velocities a Recht & Ipson best-fit curve and a confidence interval for a ballistic limit can be obtained, which is used to determine the impact resistance by defining a velocity reduction coefficient. This method can be applied to any machine guard made of ductile material. This paper validates the Recht & Ipson method by performing impact tests with a standardized 2.5 kg projectile on polycarbonate sheets of different thicknesses. Determination of the ballistic limit showed good agreement with experimental results. With the ballistic limits, the velocity reduction coefficients have been found to determine the impact resistances. Therefore, an alternative method for standardized tests to determine the impact resistance was found.

Gear Tooth Impact Testing

2003 ◽  
Author(s):  
S. B. Rao ◽  
R. C. Noss ◽  
D. R. McPherson ◽  
E. C. DeMeter
Keyword(s):  
Gear Tooth ◽  
Impact Resistance ◽  
Real Life ◽  
Impact Testing ◽  
Drop Tower ◽  
Strain Rates ◽  
Dynamic Problems ◽  
Gear Teeth ◽  
Impact Tests ◽  
The Impact

It is very difficult, if not impossible, to estimate the impact resistance of gear teeth from standard impact test data. This is because of the in-homogenous nature of most gear teeth, with a high-Carbon case and a low-Carbon core, and its complex geometry. While gears are subject to impact loading in “real life” and current research efforts are significantly focused on developing alternate materials for gears, in a variety of applications, a need to characterize the impact resistance of a gear tooth under varying strain rates has consequently arisen. In order to meet this need an existing drop tower has been modified and instrumented to test gear teeth under varying strain rates to induce various modes of fracture. This paper describes the analytical model developed to represent the drop tower and the gear holding fixture, which was utilized to evaluate various design alternatives to design a system where strain rates could be varied. Based on the results of the model, a system was implemented and a preliminary set of impact tests conducted. While some dynamic problems were encountered, these tests show that the system is performing largely as required. The source of the dynamic problems encountered was also examined and changes to the system to overcome these problems are planned. Data obtained in the impact tests conducted will also be presented to demonstrate the capability of the system.

Low Velocity Impact Resistance of CPVC Pipes Exposed to Natural Outdoor Weathering Conditions

2012 ◽  
Vol 445 ◽  
pp. 959-964
Author(s):  
Z. Khan ◽  
Necar Merah ◽  
A. Bazoune ◽  
S. Furquan
Keyword(s):  
Impact Resistance ◽  
Outdoor Exposure ◽  
Impact Testing ◽  
Low Velocity Impact ◽  
Pipe Material ◽  
Low Velocity ◽  
Impact Energies ◽  
The Impact ◽  
Impact Events ◽  
Outdoor Weathering

Low velocity drop weight impact testing of CPVC pipes was conducted on 160 mm long pipe sections obtained from 4-inch (100 mm) diameter schedule 80 pipes. Impact test were carried out for the base (as received) pipes and after their exposure to out door natural weathering conditions in Dhahran, Saudi Arabia. The results of the impact testing on the natural (outdoor exposure) broadly suggest that the natural outdoor exposures produce no change in the impact resistance of CPVC pipe material for the impact events carrying low incident energies of 10 and 20J. At the impact energies of 35 and 50J the natural outdoor exposures appear to cause appreciable degradation in the impact resistance of the CPVC pipe material. This degradation is noted only for the longer exposure periods of 12 and 18 months.

scholarly journals Effect of Thermal Ageing on the Impact Damage Resistance and Tolerance of Carbon-Fibre-Reinforced Epoxy Laminates

Polymers ◽  
2019 ◽  
Vol 11 (1) ◽  
pp. 160 ◽  
Author(s):  
Irene García-Moreno ◽  
Miguel Caminero ◽  
Gloria Rodríguez ◽  
Juan López-Cela
Keyword(s):  
Carbon Fibre ◽  
Residual Strength ◽  
Composite Structures ◽  
Impact Resistance ◽  
Thermal Ageing ◽  
Low Velocity Impact ◽  
Impact Tests ◽  
Compression After Impact ◽  
Structural Applications ◽  
The Impact

Composite structures are particularly vulnerable to impact, which drastically reduces their residual strength, in particular, at high temperatures. The glass-transition temperature (Tg) of a polymer is a critical factor that can modify the mechanical properties of the material, affecting its density, hardness and rigidity. In this work, the influence of thermal ageing on the low-velocity impact resistance and tolerance of composites is investigated by means of compression after impact (CAI) tests. Carbon-fibre-reinforced polymer (CFRP) laminates with a Tg of 195 °C were manufactured and subjected to thermal ageing treatments at 190 and 210 °C for 10 and 20 days. Drop-weight impact tests were carried out to determine the impact response of the different composite laminates. Compression after impact tests were performed in a non-standard CAI device in order to obtain the compression residual strength. Ultrasonic C-scanning of impacted samples were examined to assess the failure mechanisms of the different configurations as a function of temperature. It was observed that damage tolerance decreases as temperature increases. Nevertheless, a post-curing process was found at temperatures below the Tg that enhances the adhesion between matrix and fibres and improves the impact resistance. Finally, the results obtained demonstrate that temperature can cause significant changes to the impact behaviour of composites and must be taken to account when designing for structural applications.

scholarly journals Ultrasonic detection of spall damage induced by low-velocity repeated impact

2012 ◽  
Vol 2 (4) ◽  
Author(s):  
Naoya Nishimura ◽  
Katsuhiko Murase ◽  
Toshihiro Ito ◽  
Takeru Watanabe ◽  
Roman Nowak
Keyword(s):  
Medium Carbon Steel ◽  
Impact Testing ◽  
Acoustic Microscopy ◽  
Tensile Failure ◽  
Ductile Material ◽  
Low Velocity ◽  
Damage Development ◽  
Repeated Impact ◽  
Spall Damage ◽  
The Impact

AbstractThis paper address the examination of spall damage in medium carbon steel subjected to a repeated impact testing. The experiments were performed well below the threshold spall-stress of 2.6 GPa and the damage introduced in the subsurface volume was investigated using the low frequency scanning acoustic microscopy. Based on B- and C-scan images (the images taken along and perpendicular to the impact surface) we made a qualitative and semi-quantitative evaluation of the damage type (voids in a ductile material or cracks in a brittle one) and its distribution. We found the spall damage development dependent on the amplitude and the duration of the stress pulses. In particular, we proved that the high, long stress pulses induce damage that resembles tensile failure of material, in which voids or cracks nucleate along the spall plane to form macro-cracks. This explains why spall-damage is not seen when the first impact is below the characteristic threshold spall-stress. However, when the tests consist of more than four impacts the spall damage is produced already under stress below the threshold-value.

High and Low Speed Impact Characteristics of Nanocomposites

2015 ◽  
Vol 1105 ◽  
pp. 62-66 ◽  
Author(s):  
Saud Aldajah ◽  
Yousef Haik ◽  
Kamal Moustafa ◽  
Ammar Alomari
Keyword(s):  
High Speed ◽  
Impact Resistance ◽  
Absorption Capacity ◽  
Impact Testing ◽  
Energy Absorption Capacity ◽  
Low Speed ◽  
High Speed Impact ◽  
Bulletproof Vest ◽  
Impact Characteristics ◽  
The Impact

Nanocomposites attracted the attention of scientists due to their superior mechanical, thermal, chemical and electrical properties. This research studied the impact of adding carbon nanotubes (CNTs) to the woven Kevlar laminated composites on the high and low speed impact characteristics. Different percentages of CNTs were added to the woven Kevlar-Vinylester composite materials. An in-house developed drop weight testing apparatus was utilized for the low speed impact testing. Two different concentrations of the CNTs were added to a 15-layer woven Kevlar laminates, 0.32 wt% and 0.8 wt%. The results showed that: The 0.32 wt % CNT sample enhanced the interlaminar strength of the composite without enhancing the energy absorption capacity whereas, the 0.8 wt % CNT sample did not improve the impact resistance of the Kevlar composite.For the high speed impact tests, a bulletproof vest was prepared using woven Kevlar, resin, and CNTs at 1.5 w% percentage. The ballistic shooting was carried out by a professional shooter using a 30 caliber and 9 mm bullets for the tests. The CNT bulletproof sample bounced back the 30 caliber copper alloy bullet with no penetration.

scholarly journals Enhanced Impact-Resistance of Aeronautical Quasi-Isotropic Composite Plates Through Diffused Water Molecules in Epoxy

2020 ◽  
Author(s):  
Furqan Ahmad ◽  
Fethi Abbassi ◽  
Mazhar Ul-Islam ◽  
Frédéric JACQUEMIN ◽  
Jung-Wuk Hong
Keyword(s):  
Carbon Fiber ◽  
Impact Resistance ◽  
Composite Plates ◽  
Hot Water ◽  
Low Velocity Impact ◽  
Low Velocity ◽  
Segmental Mobility ◽  
Impact Tests ◽  
Isotropic Composite ◽  
The Impact

Abstract In order to elucidate the hygroscopic effects on impact-resistance of carbon fiber/epoxy quasi-isotropic composite plates, low-velocity impact tests are conducted on dry and hygroscopically conditioned plates, respectively, under identical configurations. For the impact tests, plates were immersed in the hot water at 80 °C to absorb a different amount of moisture content (MC). Experimental results reveal that the presence of the MC plays a pivotal role by improving the impact-resistance of composite plates. Plates with higher percentage of MC could behave elastically to a larger strain, yielding larger deflection under impact loading. From SEM fractographies, it is observed that small disbanding grows at the interface of epoxy and carbon fiber due to absorbed MC. After absorbing MC, most of impact enegy is dissipated in hygroscopic conditioned composite plates throught elastic deformation and overall less damage is induced in wet composite plates compare to the dry plate. We can postulate that the presence of MC increases the elastic limit as well as ductility of the epoxy by promoting chain segmental mobility of the polymer molecules, which eventually leads to the enhancement of the impact-resistance of wet quasi-isotropic composite plates in comparison with the dry plate.

scholarly journals DYNAMIC IMPACT WEAR AND IMPACT RESISTANCE OF W-B-C COATINGS

2020 ◽  
Vol 27 ◽  
pp. 37-41
Author(s):  
Josef Daniel ◽  
Jan Grossman ◽  
Vilma Buršíková ◽  
Lukáš Zábranský ◽  
Pavel Souček ◽  
...  
Keyword(s):  
Impact Test ◽  
Impact Load ◽  
Protective Coatings ◽  
Impact Resistance ◽  
Impact Testing ◽  
The Novel ◽  
Test Results ◽  
Dynamic Impact ◽  
Impact Deformation ◽  
The Impact

Coated components used in industry are often exposed to repetitive dynamic impact load. The dynamic impact test is a suitable method for the study of thin protective coatings under such conditions. Aim of this paper is to describe the method of dynamic impact testing and the novel concepts of evaluation of the impact test results, such as the impact resistance and the impact deformation rate. All of the presented results were obtained by testing two W-B-C coatings with different C/W ratio. Different impact test results are discussed with respect to the coatings microstructure, the chemical and phase composition, and the mechanical properties. It is shown that coating adhesion to the HSS substrate played a crucial role in the coatings’ impact lifetime.

Investigation of the Effects of Core Thickness on Low Velocity Impact Behaviors of Aluminum Honeycomb Composites

2021 ◽  
Author(s):  
Kasım Karataş ◽  
Okan Özdemir
Keyword(s):  
Sheet Material ◽  
Energy Levels ◽  
Impact Testing ◽  
Low Velocity Impact ◽  
Core Material ◽  
Low Velocity ◽  
Velocity Impact ◽  
Impact Tests ◽  
Aluminum Honeycomb ◽  
The Impact

Honeycomb structures are used where the weight to strength ratio is important. They are also preferred to absorb the energy from the blows received. In this study, low velocity impact behavior of aluminum honeycomb composites with different core thicknesses were investigated. Aluminum honeycombs used in this study are AL3003 honeycombs of 10 mm and 15 mm thicknesses. Glass fiber reinforced epoxy sheets with a thickness of 2 mm were used as the surface sheet material. Composite plates were produced by vacuum infusion method. The upper and lower face plates were cut in dimensions of 100x100 mm. The cut plates were attached to the core material with adhesive and a sandwich structure was formed. After bonding, low velocity impact tests were performed on these test samples at 40J, 100J and 160J energy levels using the composite CEAST Fractovis Plus impact testing machine. According to the results obtained from the impact tests, at higher energy levels, 15 mm thick composites have 10-15% higher energy absorption capacity than 10 mm.

scholarly journals Validation of Puncture Simulations of Railroad Tank Cars Using Full-Scale Impact Test Data

2018 ◽  
Author(s):  
Michael Carolan ◽  
Benjamin Perlman ◽  
Francisco González
Keyword(s):  
Model Validation ◽  
Transportation Systems ◽  
Full Scale ◽  
Impact Testing ◽  
Material Behavior ◽  
Fe Model ◽  
Impact Tests ◽  
Validation Criteria ◽  
Simulation Results ◽  
The Impact

The U.S. Department of Transportation’s Federal Railroad Administration (FRA) has sponsored a series of full-scale dynamic shell impact tests to railroad tank cars. Currently, there are no required finite element (FE) model validation criteria or procedures in the field of railroad tank car puncture testing and simulation. Within the shell impact testing program sponsored by FRA, comparisons made between test measurements and simulation results have included the overall force-time or force-indentation histories, the puncture/non-puncture outcomes, the rigid body motions of the tank car, the internal pressures within the lading, and the energy absorbed by the tank during the impact. While qualitative comparisons (e.g. the shapes of the indentation) and quantitative comparisons (e.g. peak impact forces) have been made between tests and simulations, there are currently no requirements or guidelines on which specific behaviors should be compared, or what measurable level of agreement would be acceptable demonstration of model validation. It is desirable that a framework for model validation, including well-defined criteria for comparison, be developed or adopted if simulation is to be used without companion shell impact testing for future tank car development. One of the challenges to developing model validation criteria and procedures for tank car shell puncture is the number of complex behaviors encountered in this problem, and the variety of approaches that could be used in simulating these behaviors. The FE models used to simulate tank car shell impacts include several complex behaviors, each of which can introduce uncertainty into the overall response of the model. These behaviors include dynamic impacts, non-linear steel material behavior, including ductile tearing, two-phase (water and air) fluid-structure interaction, and contact between rigid and deformable bodies. Several candidate qualitative and quantitative comparisons of test measurements and simulations results are discussed in this paper. They are applied to two recently-completed shell impact tests of railroad tank cars sponsored by FRA. For each test, companion FE simulation was performed by the Volpe National Transportation Systems Center. The process of FE model development, including material characterization, is discussed in detail for each FE model. For each test, the test objectives, procedures, and key instrumentation are summarized. For each set of test and simulations, several corresponding results are compared between the test measurements and the simulation results. Additionally, this paper includes discussion of approaches to model validation employed in other industries or areas of transportation where similar modeling aspects have been encountered.

scholarly journals Improved impact response of hygrothermally conditioned carbon/epoxy woven composites

2016 ◽  
Vol 23 (6) ◽  
pp. 699-710 ◽  
Author(s):  
Yucheng Zhong ◽  
Sunil Chandrakant Joshi
Keyword(s):  
Carbon Fiber ◽  
Impact Resistance ◽  
Impact Testing ◽  
Low Velocity Impact ◽  
Elastic Response ◽  
Woven Composites ◽  
Low Velocity ◽  
Hygrothermal Conditioning ◽  
The Impact ◽  
Carbon Fiber Epoxy

AbstractThe effects of hygrothermal conditioning and moisture on the impact resistance of carbon fiber/epoxy composite laminates were investigated. Specimens were fabricated from carbon fiber/epoxy woven prepreg materials. The fabricated specimens were either immersed in water at 80°C or subjected to hot/wet (at 80°C in water for 12 h) to cold/dry (at -30°C in a freezer for 12 h) cyclic hygrothermal conditions, which resulted in different moisture contents inside the laminates. It was found that the absorbed moisture did not migrate out from composite materials at -30°C. Neither of the hygrothermal conditions in this study had detrimental effects on the microstructure of the laminates. Low-velocity impact testing was subsequently conducted on the conditioned specimens. When attacked by the same level of impact energy, laminates with different moisture levels experienced different levels of impact damage. Moisture significantly alleviated the extent of damage in carbon fiber/epoxy woven laminates. The elastic response of the laminate under impact was improved after hygrothermal conditioning. The mechanism behind the improved impact resistance after absorbing moisture was proposed and deliberated.

Sign in / Sign up

Export Citation Format

Share Document