Elastic/Plastic Contact Mechanics-Based Analysis of Hard Disk Drive Media Damage From Slider Corner Impacts

2007 ◽  
Author(s):  
Raja R. Katta ◽  
Andreas A. Polycarpou ◽  
Jorge V. Hanchi
Keyword(s):  
Thin Film ◽  
Contact Mechanics ◽  
Impact Damage ◽  
Disk Drive ◽  
High Impact ◽  
Impact Model ◽  
Elastic Plastic ◽  
The Impact ◽  
Contact Parameters ◽  
Very High

A contact mechanics-based elastic-plastic impact model which considers slider corner – head disk interaction has been proposed. This model estimates the impact contact parameters accounting for the plastic deformation effects of the realistic thin-film disk media. These properties were utilized for the elastic-plastic impact model to estimate the contact parameters. Very high impact velocities and/or small slider corner radii resulted is extremely high contact depths where the disk substrate mostly dominated the impact and the effect of layers could not be seen. At lower impact velocities and higher corner radii, the impact damage was relatively smaller. The effect of the thin-film layers, which are stiffer than the substrate, was clearly observed.

Analytical and Experimental Elastic-Plastic Impact Analysis of a Magnetic Storage Head-Disk Interface

2008 ◽  
Vol 131 (1) ◽  
Author(s):  
Raja R. Katta ◽  
Andreas A. Polycarpou ◽  
Jorge V. Hanchi ◽  
Mallika Roy
Keyword(s):  
Thin Film ◽  
Impact Analysis ◽  
Hard Disk Drives ◽  
Rigid Sphere ◽  
Magnetic Storage ◽  
Impact Model ◽  
Head Disk Interface ◽  
Disk Interface ◽  
Elastic Plastic ◽  
The Impact

As the use of hard disk drives in mobile applications increases, the susceptibility of disk damage due to high velocity slider-disk impact presents a serious challenge. The impact could result in extremely high contact stresses, leading to the failure of the head-disk interface. An elastic-plastic contact-mechanics-based impact model was developed and implemented to study the impact between a slider corner and a disk. The impact model is based on the contact of a rigid sphere on a deformable half-space. The effect of slider corner radii and impact velocities on the contact parameters was initially investigated for a homogeneous disk substrate. To examine the effects of thin-film layers on the disk, the model was extended to a realistic layered disk, where the actual layered mechanical properties were directly measured. At high impact velocities and/or small slider corner radii, the impact was found to be dominated by the substrate and the effect of layers was negligible. At low impact velocities and/or large slider corner radii, the effect of nanometer thick layers could be clearly seen, as these layers are stiffer than the substrate protecting the disk from potential damage at lighter loads. Realistic dynamic impact experiments involving a slider and a spinning thin-film disk were performed using an operational shock tester. The impact damage was characterized in terms of residual penetration depth caused by the impact force of the shock and the impact velocity of the slider. However, the results were inconclusive in correlating with the impact model. To better control the experimental parameters, quasistatic nanoindentation experiments were performed on actual thin-film media and were successfully compared with the model predictions.

Impact of a Fixed-Length Rigid Cylinder on an Elastic-Plastic Homogeneous Body

2010 ◽  
Vol 132 (4) ◽  
Author(s):  
Raja R. Katta ◽  
Andreas A. Polycarpou
Keyword(s):  
Impact Damage ◽  
Element Model ◽  
Elastic Behavior ◽  
Magnetic Storage ◽  
Practical Case ◽  
Homogeneous Body ◽  
Rigid Cylinder ◽  
Elastic Plastic ◽  
Fixed Length ◽  
The Impact

A contact mechanics (CM) based model of a fixed-length rigid cylinder impacting a homogeneous elastic-plastic homogeneous body was developed and includes an improved method of estimating the residual depth after impact. The nonlinear elastic behavior during unloading was accounted for to develop an improved coefficient of restitution model. The impact model was applied to study a practical case of a cylindrical feature on the slider of a magnetic storage hard disk drive impacting the disk to predict various critical impact contact parameters. The CM model was validated using a plane strain finite element model and it was found that a cylindrical feature with a longer length results in a substantial alleviation of impact damage.

Improved Model for Impact of Viscoplastic Bodies

2016 ◽  
Vol 715 ◽  
pp. 180-185 ◽  
Author(s):  
Masniezam Ahmad ◽  
Khairul Azwan Ismail ◽  
Fauziah Mat ◽  
William James Stronge
Keyword(s):  
Plastic Deformation ◽  
Wave Propagation ◽  
High Impact ◽  
Impact Response ◽  
Stress Wave Propagation ◽  
Impact Model ◽  
Direct Impact ◽  
Proposed Model ◽  
Improved Model ◽  
The Impact

This study proposes an improved viscoplastic impact model that calculates impact response for direct impact between two compact bodies. The proposed model employs spring and viscous elements that represent the energy loss due to plastic deformation and stress wave propagation, respectively. The impact response is calculated by solving differential equations through analytical and numerical methods. This model can accurately predict impact response for low, moderate and high impact speeds.

scholarly journals The impact of errors in medical certification on the accuracy of the underlying cause of death

PLoS ONE ◽  
2021 ◽  
Vol 16 (11) ◽  
pp. e0259667
Author(s):  
U. S. H. Gamage ◽  
Tim Adair ◽  
Lene Mikkelsen ◽  
Pasyodun Koralage Buddhika Mahesh ◽  
John Hart ◽  
...  
Keyword(s):  
Cause Of Death ◽  
Death Certificate ◽  
International Classification Of Diseases ◽  
High Impact ◽  
Error Type ◽  
Medical Certification ◽  
Underlying Cause Of Death ◽  
The Impact ◽  
Very High ◽  
Death Data

Background Correct certification of cause of death by physicians (i.e. completing the medical certificate of cause of death or MCCOD) and correct coding according to International Classification of Diseases (ICD) rules are essential to produce quality mortality statistics to inform health policy. Despite clear guidelines, errors in medical certification are common. This study objectively measures the impact of different medical certification errors upon the selection of the underlying cause of death. Methods A sample of 1592 error-free MCCODs were selected from the 2017 United States multiple cause of death data. The ten most common types of errors in completing the MCCOD (according to published studies) were individually simulated on the error-free MCCODs. After each simulation, the MCCODs were coded using Iris automated mortality coding software. Chance-corrected concordance (CCC) was used to measure the impact of certification errors on the underlying cause of death. Weights for each error type and Socio-demographic Index (SDI) group (representing different mortality conditions) were calculated from the CCC and categorised (very high, high, medium and low) to describe their effect on cause of death accuracy. Findings The only very high impact error type was reporting an ill-defined condition as the underlying cause of death. High impact errors were found to be reporting competing causes in Part 1 [of the death certificate] and illegibility, with medium impact errors being reporting underlying cause in Part 2 [of the death certificate], incorrect or absent time intervals and reporting contributory causes in Part 1, and low impact errors comprising multiple causes per line and incorrect sequence. There was only small difference in error importance between SDI groups. Conclusions Reporting an ill-defined condition as the underlying cause of death can seriously affect the coding outcome, while other certification errors were mitigated through the correct application of mortality coding rules. Training of physicians in not reporting ill-defined conditions on the MCCOD and mortality coders in correct coding practices and using Iris should be important components of national strategies to improve cause of death data quality.

The Effect of the Impact Model on Vibration Response of Discrete and Continuous Systems

2012 ◽  
Author(s):  
M. R. Brake
Keyword(s):  
Constitutive Model ◽  
Coefficient Of Restitution ◽  
Degree Of Freedom ◽  
Impact Dynamics ◽  
Impact Model ◽  
Single Degree Of Freedom ◽  
Elastic Plastic ◽  
Single Degree ◽  
Contact Models ◽  
The Impact

Impact is a phenomenon that is ubiquitous in mechanical design; however, the modeling of impacts in complex systems is often a simplified, imprecise process. In many high fidelity finite element simulations, the number of elements required to accurately model the constitutive properties of an impact event is impractical. As a result, rigid body dynamics with approximate representations of the impact dynamics are commonly used. These approximations can include a constant coefficient of restitution, an artificially large penalty stiffness, or a single degree of freedom constitutive model for the impact dynamics that is specific to the type of materials involved (elastic, plastic, viscoelastic, etc.). In order to understand the effect of the impact model on the system’s dynamics, simulations are conducted to investigate a single degree of freedom, two degrees of freedom, and continuous system each with rigid stops limiting the amplitude of vibration. Five contact models are considered: a coefficient of restitution method, a penalty stiffness method, two similar elastic-plastic constitutive models, and a dissimilar elastic-plastic constitutive model. Frequency sweeps show that simplified contact models can lead to incorrect assessments of the system’s dynamics and stability. In the worst case, periodic behavior can be predicted in a chaotic regime. Additionally, the choice of contact model can significantly affect the prediction of wear and damage in the system.

Second Paper: Extrusion of Steel and Titanium

1967 ◽  
Vol 182 (1) ◽  
pp. 188-202 ◽  
Author(s):  
E. R. Austin ◽  
R. Davies ◽  
F. Bakhtar
Keyword(s):  
Impact Velocity ◽  
High Impact ◽  
Velocity Range ◽  
Backward Extrusion ◽  
Forward Extrusion ◽  
High Speeds ◽  
Extruded Product ◽  
Work Of Deformation ◽  
The Impact ◽  
Very High

This paper describes the results of forward and backward extrusion tests on steel and titanium specimens at very high impact speeds, using reductions in area of 44 to 86 per cent. The specimens were in all cases of 1-in diameter, 1.5 in long. For the cold forward extrusion of steel, impact speeds over the range 68-310 ft/s were used. Comparison of mean extrusion and work of deformation at these high speeds was made with the values arising at very low speed. Extrusion pressures were minimal in the impact velocity range 40-80 ft/s. Tests using steel billets preheated to temperatures between 300 and 600°C showed no great advantage in preheating above 400°C. This degree of preheating showed considerable advantages over the cold process, in that extrusion pressures were much reduced, product quality was improved, and higher extrusion ratios could be obtained. Limited backward extrusion tests at 66 ft/s proved the feasibility of the process. Gold forward extrusion of titanium at 65 and 167 ft/s was successful only at the relatively low reductions in area of 44 and 61 per cent. At higher degrees of deformation, the extruded product broke into small pieces.

Energy Absorbing Characteristics of a Graded Honeycomb Structure Under Impact

2008 ◽  
Author(s):  
Muhammad Ali
Keyword(s):  
Impact Damage ◽  
Honeycomb Structure ◽  
High Impact ◽  
Banana Peel ◽  
Primary Concern ◽  
Confined Space ◽  
Protection Systems ◽  
Crash Protection ◽  
Energy Absorbing ◽  
The Impact

Energy absorption is becoming a challenging issue in various applications where safety is a primary concern. Increasing demands on crash protection systems in the arena of public safety confirms the need for superior energy absorbing materials and structures to meet stringent requirements for alleviating the impact damage. In this paper, a compact energy absorbing honeycomb structure is presented; the structure is reproduced from the graded cellular geometry observed in a banana peel. The energy absorbing characteristics of the structure at high impact velocities are studied by means of non-linear dynamic finite element simulations using ABAQUS. The structure mitigates impact in a confined space through a uniform layer wise collapsing mechanism. As compared to static and low dynamic cases, an increase in the crushing strength of the structure is observed for high impact loads. An analytical model is presented, which predicts the behavior of the structure adequately for high impact velocities.

Fast Clustering Environment Impact using Multi Soft Set Based on Multivariate Distribution

2021 ◽  
Vol 5 (3) ◽  
pp. 291
Author(s):  
Iwan Tri Riyadi Yanto ◽  
Ani Apriani ◽  
Rahmat Hidayat ◽  
Mustafa Mat Deris ◽  
Norhalina Senan
Keyword(s):  
Distribution Function ◽  
Public Perception ◽  
High Impact ◽  
Soft Set ◽  
Multivariate Distribution ◽  
Environment Impact ◽  
Development Activity ◽  
Total Data ◽  
The Impact ◽  
Very High

Every development activity is always related to human or community aspects. This can also lead to changes in the characteristics of the community. The community's increasing awareness and critical attitude need to be accommodated to avoid the emergence of social conflicts in the future. This research is to find out how the public perception about the impact of development on the environment. Two methods are used, i.e., MDA (Maximum Dependency Attribute) and MSMD (the Multi soft set multivariate distribution function). The MDA is to determine the most influential attribute and the Multi soft set multivariate distribution function (MSMD) is to group the selected data into classes with similar characteristics. This will help the police producer plan the right mediation and take quick activity to make strides in the quality of the social environment. The experiment conducted level of impact based on the clustering results with the greatest number of member clusters is cluster 1 (very low impact) with 32.25 % of total data following cluster 5 (Very High impact) with 24.25 % of total data. The experiment obtains the level of impact based on the clustering results. The greatest number of member clusters is cluster 1 (extremely low impact) with 32.25 % of total data following cluster 5 (Very High impact) with 24.25 % of total data. The scatter area impact is spread at districts 6, 7, 10, 11, the most of very high impact and districts 1,2,3,4,5,8 the lowest impact. 

Impact damage in brittle materials in the elastic-plastic response régime

1978 ◽  
Vol 361 (1706) ◽  
pp. 343-365 ◽  
Keyword(s):  
Impact Damage ◽  
Strength Degradation ◽  
Impact Fracture ◽  
Impact Dynamics ◽  
Plastic Response ◽  
Principal Characteristics ◽  
Elastic Plastic ◽  
Contact Behaviour ◽  
Mechanics Concepts ◽  
The Impact

The impact fracture created in the elastic-plastic response régime has been characterized in terms of its surface extension and penetration. A numerical dynamic analysis has been performed of a typical impact within this régime to indicate some of the principal characteristics of the contact behaviour and the stress field. The damage has then been analysed, by using simplified postulates based on key features of the impact dynamics and basic fracture mechanics concepts. This has enabled the primary material and target parameters affecting the impact fracture to be identified. Thereafter, some implications for strength degradation and erosion have been discussed.

On the Use of an Elastic-Plastic Contact Law for the Impact of a Single Flexible Link

1995 ◽  
Vol 117 (4) ◽  
pp. 527-533 ◽  
Author(s):  
A. S. Yigit
Keyword(s):  
Impact Force ◽  
Body Motion ◽  
Model Parameters ◽  
Impact Model ◽  
Flexible Link ◽  
Continuous Transition ◽  
Flexible Links ◽  
Elastic Plastic ◽  
The Impact ◽  
Impact Models

An elastic-plastic contact law is proposed for modeling impact of a single flexible link. This contact law allows continuous transition between contact and noncontact phases and is capable of predicting impact force histories. The impact model parameters can readily be obtained from the material and geometric properties. Excellent agreement with the experimental results has been obtained for both elastic and rigid body motion of the link. The impact force histories are also obtained and compared for perfectly elastic and elastic-plastic impact models. It is shown that a perfectly elastic impact assumption is not realistic for most impacts of flexible links.

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