Technical Journal

Technical Papers

• Development of Bearings with Insulating Coating to Resist Electrical Corrosion in HEV/EV Units
• How Hub Unit Bearings Contribute to Carbon Neutrality
• Development of Magnetostrictive Torque Sensor
• Evaluation of Steering Feel in the Off-Center Range Using Physiological Characteristics
• Trends in Bearings for Steelmaking Equipment
• QuickStopBearing? for Dental Air Turbines
• Evaluation of Lubrication Performance in Ball Screws and Linear Guides by the Electrical Impedance Method
• NSK VIRTUAL EXPO
• Study on Simple Vibration Prediction Method for Permanent Magnet Synchronous Motors and Applications
• Establishment of an Integrated Automated Embryonic Manipulation System for Producing Genetically Modified Mice

New Products

• Ball Bearings with Labyrinth Seal for Transmission Applications
• BOC Bearings with Resistance to Wear from Creep
• Development of Gen 4 High-Speed Ball Bearings for HEVs/EVs
• Large-Size T-HUB 1 Bearings for Trucks
• Next-Generation Long-Life Planetary Shafts (SHJ7)
• Drawn Cup Needle Roller Bearings with Large Diameter for Electric/Hybrid Vehicles
• Column EPS with Steering Wheel Angle Detection
• NSK Verify (Bearing Information Acquisition Service Using 2D Barcode)
• Bioplastic Cage for Deep Groove Ball Bearings
• High Load Capacity Angular Contact Ball Bearings with Pressed Steel Cage (BEAW)

Technical Papers

• Ball Screw Technologies to Control Machine Tool Quadrant Glitches
• Technical Trends in Bearings for Papermaking Machine
• Development of High-Speed Ball Bearings for Hybrid Electric Vehicles (HEVs) and Electric Vehicles (EVs)
• Hub Unit Bearing Design Using Digital Twins
• Introduction of Analysis Method Automation Technology for Efficient Design
• Estimation of Noise Radiation Including Airborne Noise Using the In-situ Blocked Force Approach(Third Report, Experimental Verification of the Estimation Method by Application to Rattle Noise From an Electric Power Steering System)
• Fracture Mechanics-Based Criteria for Fatigue Fracture of Rolling Bearings under the Influence of Defects
• Enhancement of Weldline Strength by Applying a Reservoir to the Plastic Cage of a Rolling Bearing
• SuperLimbs for Sit-to-Stand Support and Fall Prevention

New Products

• ROBUSTDYNA™ High Load Capacity Ultra-High-Speed Angular Contact Ball Bearings
• Large Spherical Roller Bearings with Smearing Preventative (NSK DLC Coating)
• Low-Maintenance High-Reliability Gearbox Bearings for Railways
• NSK Linear Guides™ Long-Life Series: DH/DS Models
• Wireless Vibration Diagnostic Device Model D-VibA10
• Condition Monitoring Application Software ACOUS NAVI™ (FIELD System)
• High Efficiency Tapered Roller Bearings for Powertrains
• Pressed Angular Contact Ball Bearings for Electric and Hybrid Vehicles
• Thrust Needle Roller Bearings with Electrical Corrosion Resistance

Technical Papers

• Development of Tapered Roller Bearings for Electric/Hybrid Vehicles
• Demonstration of Two-Speed Seamless Shifting for EV Using Magnetostrictive Torque Sensor
• Developments in Steering Performance for Automotive Steering Systems
• Development of Bearings for Industrial Machinery Motors
• High Load Endurance Test Unit for Electric Injection Molding Machine Ball Screws
• Mobile Extendable Robot Arm (MERA)
• Development of an Automated Single-Cell Seeding Device for Biopharmaceuticals
• Quantitative Evaluation of Effects on Dent-Initiated Flaking of Rolling Bearings(Part 1: Evaluation of Dent-Density ρd)
• Quantitative Evaluation of Effects on Dent-Initiated Flaking on Rolling Bearings(Part 2: Evaluation of Factors Influencing Dent-Density ρd)

New Products

• Hub Unit Bearing Sealed by a Plastic Sensor Cap
• Ball Screw Units for Electric Hydraulic Brake Systems
• High Safety Redundant Column EPS
• Thin-Section Ball Bearings for Strain Wave Gearings
• Sealed-Clean Four-Row Tapered Roller Bearing with Long-Life, Water-Resistant Grease
• High Durability Precision Ball Screw

Technical Papers

• Development of NSK LCube II™ Tapered Roller Bearings for Electric-Hybrid Vehicles
• Technologies of NV Measurement and Analysis for Steering Systems
• Development of Long Life Ball Screw using Material with High Retained Austenite Amount γR for High-Load Drive
• Improved Reliability of Roller Guides for Machine Tools
• Effect of Small Defect on the Flaking Strength of Rolling Bearings (Part 1: FEM analyses of stress intensity factor KII under rolling contact)
• Effect of Small Defect on the Flaking Strength of Rolling Bearings (Part 2: Evaluation of the flaking strength of rolling bearing having a small drilled hole based on the stress intensity factor)
• Low Torque Technologies for Rolling Bearings with Grease Lubrication
• X-Ray CT Imaging of Grease Behavior in Ball Bearing and Numerical Validation of Multi-Phase Flows Simulation
• Rolling Bearing Diagnosis Based on Deep Learning Enhanced by Various Dataset Training

New Products

• Long Life Material for Local Procurement (SHJ7)
• High-Performance Tapered Roller Hub Unit Bearings for Automobiles
• Low-Noise Thrust Needle Roller Bearing
• High-Performance Low-Friction Seal for Single-Row Deep Groove Ball Bearings
• Lightweight High-Performance Intermediate Shaft
• Touchdown Bearings for the Superconducting Flywheel Power Storage System
• NSK K1-L Lubrication Unit

Preface

• NSK's Latest Technologies and Products for Industrial Machinery

Technical Papers

• Approach of Condition Monitoring in Industrial Machinery
• Technical Trend of Industrial Machinery Bearings
• Technical Trend of Wind Turbine Bearings
• The Technical Trend of Machine Tool Components
• Technical Trends of Railway Products
• ISO 13482 certificated and practical application of Guidance Robot LIGHBOT
• Development of Omnidirectional Mobile Electric Wheels
• Analysis Prediction Technique of Flaking Expansion in Roller Bearings for Wind turbines.
• Simultaneous Measurement of Oil Film Thickness and Breakdown Ratio in EHD Contacts-Verification of Electrical Impedance Method

New Products

• Wireless Vibration Diagnostic Device Bearing Doctor Model BD-2
• Low-Torque Ball Bearings for High-Efficiency Motors
• Optimized Long-Life Cylindrical Roller Bearings for Continuous Casting Machines
• Large (TL) Spherical Roller Bearings Resistant to Inner Ring Fracture for Paper Machines
• Vibration Control Actuator for Train Cars

Preface

• Automotive Products and Technologies

Technical Articles

• Transmission-Equipped Wheel Hub Motor Consisting of Two Electric Motors and the Performance Evaluation
• Estimation of Traction Curves under Practical Operating Conditions
• Improving the Efficiency of Derivative Development through Systematic Restructuring
• Weight Reduction of Column-Type EPS through Gearbox Thinning
• Recent Technical Trends in Hub Unit Bearings
• Low-Friction Technology for Tapered Roller Bearings
• CFD Analysis of Tapered Roller Bearings and Ball Bearings for Reducing Agitation Torque
• Enhanced Performance of Rolling Bearings by Improving the Resistance of Rolling Elements to Surface Degradation
• Relationship between Supplied Oil Flow Rates and Oil Film Thicknesses under Starved Elastohydrodynamic Lubrication

New Products

• BELTOP8 High-Reliability and Low-Friction Ball Bearings for CVTs
• Super-Long-Life Needle Rollers for Automobile Transmissions
• Plastic Pin Internal Contractile Steering Column

Preface

• NSK Commemorates its Centennial

Technical Articles

• Advanced Technology for Lubricant Film Formation by Grease and Application to Improve Bearing Wear Resistance under Severe Conditions
• White Structure Flaking in Rolling Bearings for Wind Turbine Gearboxes
• Development of New-Type Oxide Ceramic Ball for Bearings
• Correlations Between the Porosity and Friction Performance of Wet Friction Materials
• Development of a High-Power Two-Roller Traction Tester and Traction Curve Measurement
• New Technologies for Bearings in Electric Vehicle and Hybrid Electric Vehicle Powertrains
• NSK EPS Control Technology
• Development of High-Speed
• Development of a High-Precision Vertical-Axis Table

New Products

• Ball Bearings with Excellent Sealing Performance for Fan Clutches
• New Ball Bearing with a Retainer Plate for Automobile Transmissions
• The World's Lightest Electric Power Steering System
• spaceaCRYO: New High-Performance Ceramic Ball Bearings for Liquefied Gas Pumps
• Spherical Roller Bearings Featuring High Reliability and Excellent Sealing Performance for Conveyor Pulleys in Mines
• Ball Bearings for Ultra-High-Speed Rotary Motors
• ROBUSTSHOT Bearings: Direct Lubrication Angular Contact Ball Bearings for Machine Tool Spindles
• Ultra-Large Ball Screws

Technical Articles

• visualization of lubricating grease in ball bearing using x-ray ct and validation of digital simulation
• visualization of grease behavior in a ball bearing using x-ray
• low torque technology using grease and application to motor bearings
• water resistant technology for grease and application to bearings
• development of bearing units with torque sensors for automotive transmissions
• development of automotive transmission thrust needle roller bearings with integrated washer and oil flow control
• development of low-friction grease for eps worm reduction
• development of micro manipulation system
• strategy for frictional behavior control in ball screws

New Products

• high-reliability clutch release bearings for emerging markets
• compact
• idler/tensioner bearings with high-speed capability and excellent sealing performance
• dental air turbine bearings
• long-life
• nsktac03 nskhps angular contact thrust ball bearings for ball screw support in high-load drive applications
• ball screws with minimal grease-splatter l1 seals
• toughcarrier
• nh series and ns series nsk linear guides: more than twice the life of conventional nsk linear guides
• megatorque motor pb series

Preface

• NSK's Latest Technologies and Products for Industrial Machinery

Technical Articles

• Prismless Surface Plasmon Resonance (P-SPR) Sensor Using Periodic Nanostructures
• Bearing Torque Characteristics of Lithium Soap Greases with Some Synthetic Base Oils
• Evaluation of Lubrication Properties of the 100 % Food-Derived Grease for Rolling Bearings
• Increasing Sizes of Wind Turbines and Bearing Trends
• Technological Trends of Bearings for Industrial Compressors
• Development of the TOUGHCARRIER for Automotive Manufacturing Equipmen
• Development of a Nut Cooling Ball Screw

New Products

• Ultra-High-Speed Precision NSKROBUST Angular Contact Ball Bearings for Main Spindles of Machining Centers
• Long-Life Thrust Ball Bearings with a Highly Reliable Cage for Agricultural Machinery HSTs
• Cylindrical Roller Bearings for Centrifugal Chillers
• BNEQARTET—Long-Life Ball Bearings for Washing Machines
• SPACEA Series—Solid-Lubricant-Coated Bearings for High Temperatures
• Ball Screws with X1 Seals for Machine-Tool Applications
• HTF-SRE Large, High-Speed, High-Load Capacity Ball Screws
• NSK Roller Guides Equipped with V1 Seals
• Random-matching, High-Precision-Grade RA Series Roller Guides

Technical Articles

• The Effects of Hydrogen on Microstructural Change and Surface Originated Flaking in Rolling Contact Fatigue
• Efficiency Improvement in Half-Toroidal CVTs
• Improvement of Efficiency in Half-Toroidal CVTs

New Products

• Deep Groove Ball Bearings with a Retainer Plate for Transmissions
• Hub Unit Bearing with High-Performance Sealing and a Nonmagnetic Metallic Cap
• Low-Friction Torque Tappet Roller Bearings for Automotive Engines

Technical Articles

• Coupled Simulation of Starved Elastohydrodynamic Lubrication and Liquid Film Flow
• Differences in Preventive Mechanisms for Fretting Wear between Oil and Grease Lubrication
• Development of a Robot Substitute for a Guide Dog
• Technological Trends of Jet Aircraft Engine Bearings
• Technology Development and Future Challenge of Machine Tool Spindle
• Electrical Erosion of Motor Bearings
• Development of Long-Life Planetary Shaft (SHX3 Steel) for Planetary
• Gears of Automotive Transmissions

New Products

• Shinkansen Axle Cylindrical Roller Bearings for E5 Series Bullet Train
• High-Performance Standard NSKHPS Large-Size Spherical Roller Bearings
• Energy-Saving HALFRICTION Ball Bearings for High-Efficiency Motors
• High-Performance, Shielded Double-Row Angular Contact Ball Bearings for Industrial Water Pumps
• NSKROBUST Series Type E of Angular Contact Ball Bearings for Machine Tools
• SPACEA Series—Highly Corrosion Resistant and High-Hardness Stainless Steel ESZ Bearings
• Ultrahigh-Speed, Large-Diameter Ball Bearing for Hybrid Car Motors
• Highly Reliable, Lower Frictional Torque Ball Bearings for Belt-Type CVTs
• Silent Needle Roller Bearing for Automotive Electrical Components
• Automotive Transmission Thrust Needle Roller Bearings with Integrated Washer and Oil-Flow Control
• HMS Series of Ball Screws for High-Speed Machine Tools
• Miniature Large-Lead Series of High-Speed, Low-Noise Ball Screws
• Precision-Grade, Medium-Preload, Random-Matching NSK Linear Guides
• Random-Matching, Miniature PU and PE Series of NSK Linear Guide
• Highly Durable, Highly Rigid, Slidable Intermediate Shaft for EPS
• Wedge Gear of New Positive-Lock Mechanism for Steering Column
• Megapositioner of Highly Rigid, Ultralarge-Torque-Output, Rotary Positioning Units
• PX Series of High-Acceleration Megatorque Motors

Partial Special Issue of Automobile Products

Preface

• NSK's Automotive Products

Technical Articles

• Development of Ultrahigh-Speed Ball Bearings for Motors in Next-Generation Hybrid Vehicles
• Development of New-Generation Low-Frictional-Torque Tapered Roller Bearings
• Development of Ultralow-Torque Ball Bearings for Hybrid Vehicles
• Development of Low-Torque Thrust Needle Roller Bearing for Automotive Air Conditioner Compressors
• Development of Low-Torque Hub Unit Bearings
• Technological Trends of Bearings for Electric Motors on Board Vehicles

New Products

• Ultrahigh-Speed Ball Bearing for Motors and Power Generators in Next-Generation Hybrid Vehicles
• Ultralow-Torque Sealed-Clean Ball Bearings for Transmissions
• High-Speed-Type Miniature Roller & Cage Assembly for Planetary Gears
• Long-Life Thrust Needle Roller Bearings Using Alternative Material to SK85
• High-Strength, Pressed-Steel Pulley
• Newly Developed, Highly Durable Clutch Pulley Unit
• Electric Power Steering System for Excellent On-Center Steering Feel
• Ball Screw for Motorcycle Brake Systems

Technical Articles

• Mechanism of Dent Initiated Flaking and Bearing Life Enhancement Technology under Contaminated Lubrication Condition
  Part I: Effect of Tangential Force on Dent Initiated Flaking
  Part II: Effect of Rolling Element Surface Roughness on Flaking Resulting from Dents, and Life Enhancement Technology of Rolling Bearings under Contaminated Lubrication Condition
• Oil Film Behavior under Minute Vibrating Conditions in EHL Point Contacts
• Development of ROBUSTSLIM Series of Low-Profile Angular Contact Ball Bearings for Swivel Units in Machine Tools

New Products

• Smear-Resistant Spherical Roller Bearings for Papermaking Machinery
• High-Performance Bearings for Satellite Attitude Control Reaction Wheels
• Slight-Preload Type RA Series Roller Guides of NSK Linear Guides

Technical Articles

• Temperature Rise Analysis in Traction Contact Areas of Toroidal CVTs^*
  —Influence of Half-Cone Angle on Temperature Rise
• Microstructural Development in Bearing Steel during Rolling Contact Fatigue
  Improvements of Half Toroidal CVT^*
• Development of World's Thinnest Drawn-Cup Needle Roller Bearings with Seal Ring
  —The Need for Improved Fuel Economy and the Application of Needle Roller Bearings
• Technological Trends in Linear Motion Rolling Guides for Machine Tools

New Products

• Thrust Needle Roller Bearings with Retention Tabs
• Cartridge-Type Ball Bearings for Turbochargers
• High-Performance Standard NSKHPS Angular Contact Ball Bearings for Industrial Machinery
• Low-Torque, Highly Rigid, Thin-Section, Angular Contact Ball Bearings Fitted with Outer Seals
• General-Purpose, Shielded Deep Groove Ball Bearings with High Load Capacity
• Highly Reliable & Long-Life Split Cylindrical Roller Bearing Units for Segmented Drive Rolls
• TW Series of Ball Screws for Twin-Drive Systems
• HMD Series of Ball Screws for High-Speed Machine Tools
• RB Series Roller Guides of NSK Linear Guides

* These articles have been published on this website with permission from the Society of Automotive Engineers of Japan (JSAE). These articles may not be printed as they have been translated and/or reprinted with permission from JSAE.

Special Issue of Products Supporting Daily Life and Industry

Special Articles

• Preface
• Technological Trends of Railway Rolling Stock Bearings
• Technological Trends of Bearings for Construction Machinery
• Bearing Technology for Industrial Compressors
• Technological Trends of Ball Screws for Industrial Machinery
• Technological Trends of NSK Linear Guides for Industrial Machines
• Technological Trends of Ball Bearings for Household Electrical Appliances
• Development of a Plastic Cage for High-Performance, Electric Motor Ball Bearings
• Research of Electrically Conductive Grease for Office Equipment Bearings

New Products

• Sensor Bearings for Railway Rolling Stock Axles
• ELCOMP Bearings Series for Screw Compressors in Industrial Applications
• High-Performance Angular Contact Ball Bearings for Industrial Machinery Pumps
• Quiet & Low-Vibration Series of Spherical Roller Bearings for Elevator Applications
• Creepfree Bearings for Fan and Pump Motors
• Low-Friction Bearings that Promote Energy Efficiency of Vacuum Cleaner Suction Motors
• Quiet-Running Long-Life Ball Bearings for Fan Motors Operating in High-Temperature Environments
• BSL Series of Ball Screws for Small Lathes
• HTF-SRD Series of Long-Lead Ball Screws for High-Speed and Heavy-Load Applications
• High-Accuracy HS Series of Ultra-Precision NSK Linear Guides
• NSK Linear Guides for Food Processing Equipment and Medical Devices

Technical Articles

• Unique Fatigue Failure of Spherical Roller Bearings and Life-Enhancing Measures
  Part II : Long-Life Theory of NSKHPS Spherical Roller Bearings
• Power Loss Factor Analysis of the High-Power Output EPS System
• Development of the Next-Generation Half Toroidal CVT —Power Transmission Efficiency and Control of the Geared Neutral System
• Sensor Bearing Development
• Development of a High-Output Brushless DC Motor for EPS
• Development of Bearings for Robots in Vacuum Environments
• Development of the NSK RA Series of Roller Guides

Technical Articles

• Unique Fatigue Failure of Spherical Roller Bearings and Life-Enhancing Measures
  Part I : Unique Fatigue Failure of Spherical Roller Bearings
• Bearing Outer Ring Creep
• Latest Developments in Thin-Film Lubrication Technology for Vacuum and Clean Environments
• Development of Nanopositioner
• Development of Ultrahigh-Speed Planetary Needle Roller Bearings
• Development of Thrust Needle Roller Bearing with Wear-Resistant & High-Strength Cage

Technical Articles

• Development of the Next-Generation Toroidal CVT
  —Geared Neutral and Power-Split System for 450 N·m Engines
• High-Performance Standard Roller Bearings
  —NSKHPS Spherical Roller Bearings
• Pulley Support Bearings for Push-Belt CVTs
• Long-Life Materials Countering White Structure Flaking
• Research Work for Clarifying the Mechanism of White Structure Flaking and Extending the Life of Bearings

• Technology of Highly Reliable Bearings for Wind Turbine Gearboxes
• Bearing Technologies for Centrifugal Pumps
• Trends of Bearing Technology in Iron and Steel Industries
• Automatic Grease Replenishing System for Machine Tool Main Spindles — Fine Lub II
• S3 Ball Screws: Super Low-Noise Ball Screws for Automation Equipment
• Development of New Series of Megatorque Motor Series for High Speed and Precise Positioning

• Trends and New Technologies of Hub Unit Bearings
• Simulation Technology for Developing EPS Brushless Motors
• Latest Trends and Technologies of Automotive Electrical Component Bearings
• Low Frictional Torque Technology of Rolling Bearings
• Latest Technologies Applied to AT Maji-Band
• Trends and New Technologies of Automatic Transmission Bearings
• Efficiency Analysis of Half-Toroidal CVT Considering Deformation of Pivot Shaft

• Latest Trends in Machine Tool Spindles and Bearing Technology
• Development of Integrated Motor Spindle Unit for Machine Tools Using Automatic Grease Replenishing System
• Development of High-Speed and Low-Noise Ball Screws
• Numerical Analysis Technology & NSK Linear Guides for Machine Tools

• Hub Unit Bearings with ABS Sensor
• Development of NSK ABLE Forecaster
• Long Life Bearing Technology by Carbonitriding
• Research of Auxiliary Landing Bearings for Turbo Molecular Pumps
• Electrically Conductive Bearing Grease for Office Equipment

• Development of Water-Tough (WTF) Bearings for Steel Mills — Longer Life in Harsh Environments
• Non-Magnetic and Highly Corrosion-Resistant Titanium Alloy Bearings
• Development of New High-Capacity Cylindrical Roller Bearings
• Super Precision Cylindrical Roller Bearings
• Development of the Next-Generation Half-Toroidal CVT
• Development of Wedge Roller Traction Drive Units
• High Straightness Positioning Stage Implementing Real-time Position Compensation

• Development of Silent-running Cylindrical Roller Bearings
• Development of the Super Wear-Resistant (SWR) Bearing
• Pressed Rocker Arm
• Development of Double-Row Bearings for Automatic Transaxles
• Development of Low-Noise NSA Grease for Fan Motor Bearings
• Development of HTF Series Ball Screws for High Load Drive Application

• Activities Towards Environmentally Friendly Products
• NSK Products and Technologies Contribute to Energy Conservation
• Development of NSK's Extremely Quiet, Low-Torque, GR Series Ball Bearings
• NSK Products and Technologies for Preserving Natural Resources
• NSK Products and Technologies for Promoting a Cleaner Environment while Preserving Natural Resources
• NSK Products and Technologies Contributing to Low Noise and Low Vibration

• Development of New Life Equation for Ball and Roller Bearings
• Development of the Half-Toroidal CVT POWERTOROS Unit (3)
  — Development of the Power-Split System
• Automobile Transmission Performance and Bearing Type
• Development of NSK S1 Series Ball Screws and Linear Guides

• Development of POWERTOROS Unit Half-Toroidal CVT (2)
• Development of Hub Unit Bearing with Swaging
• An Auto-Tensioner for Timing Belts
• Development of High-Speed Cylindrical Roller Bearings for Machine Tools

• EA Spherical Roller Bearings
• ROBUST Series High-Speed Precision Angular Contact Ball Bearings for Machine Tool Spindles
• Development of the POWERTOROS UNIT Half Toroidal CVT
• Recent Developments in Highly Precise NSK Linear Guides

• Development of NSK Extra-Capacity Sealed-Clean Roll Neck Bearings for Rolling Mills
• Ball Screw with Rotating Nut and Vibration Damper
• Ceramic Bearings for Special Environments
• Excellent Stainless Bearing Steel (ES1)
• Development of NSJ2 Bearing Steel

• SPACEA Series Products for Special Environments
• Bearings for Traction Gears
• Inner Ring Fracture Characteristics under Rolling Contact
• ABS Motor/Actuator Bearing Development for Applications Which Require Brake Fluid Compatible Contact Seals
• High-Performance Ball Bearings for Fan Motors in the Chinese Market

• Bearings for Aircraft Gas Turbine Engines (part 2)
• Electric Power Steering (EPS)
• Recent Development of NSK Direct-Drive Motors
• New Electronic NSK Product Guide
• Sound and Vibration in Rolling Bearings

• Bearings for Aircraft Gas Turbine Engines (part 1)
• Development of NSK Linear Guides
• Rear-wheel Bearings for Fully Floating Axles—Analysis of Load and Optimum-strength Design
• Rolling Bearings for Hard Disk Spindle Motors
• Development of the NSK K1 Seal for Linear Guides

• Recent Technical Trends in Ball Screws
• Research and Development of Bearings for Special Environments
• Performance of Large-size Spherical Thrust Roller Bearings at High Speed
• High-performance Ball Bearings for Automotive Alternator Applications
• Analysis of Steering Column Vibration